1. Field
The presently disclosed subject matter relates to a vehicle headlight and a headlight system using the same, and more particularly to a vehicle headlight using a semiconductor light source and a mirror that can provide various light distribution patterns while having a simple structure and the headlight system using the same that can vary a light distribution pattern in accordance with surroundings such as an oncoming vehicle, a forward travelling vehicle, a road, etc.
2. Description of the Related Art
Vehicle headlights that can vary a light distribution pattern to maintain a high visibility in accordance with surroundings such as an existence of an oncoming vehicle, a forward travelling vehicle and the like have been developed in recent years. A conventional vehicle headlight using variable shades is disclosed in Patent Document No. 1 (Japanese Patent Application Laid Open JP2009-211963). FIG. 9a is a schematic side cross-section view showing this right and left conventional vehicle headlight, and FIG. 9b is a rear view showing a right and left variable shade used in the right left conventional vehicle of FIG. 9a. 
The conventional vehicle headlight 100 includes: a reflector 101 having a first focus and a second focus; a discharge lamp 102 located near the first focus of the reflector 101; a variable shade 104 in which a top edge of the variable shade 104 is located near the second focus of the reflector 101; a projector lens 103 projecting light emitted from the discharge lamp 102 in a light-emitting direction of the vehicle headlight 100; and an actuator 105 slanting the variable shade 104 toward the projector lens 103 and the discharge lamp 102.
The variable shade 104 can include a right variable shade 104R composed of a right shade 104RR and a left shade 104RL and can be used for a right headlight of the vehicle headlight 100. A left variable shade 104L composed of a right shade 104LR and a left shade 104LL can be used as the variable shade 104 for a left headlight of the vehicle headlight 100. The right variable shade 104R and the left variable shade 104L shown in FIG. 9b are rear views from the discharge lamp 102.
FIG. 10 is a plurality of schematic diagrams depicting exemplary light distribution patterns formed by the vehicle headlight of FIG. 9a. When the vehicle headlight 100 is lit by a manual switch, pattern (a) of a low beam is formed by locating the right and left variable shades 104R, 104L at a vertical mode as shown in FIG. 9a. When pattern (b) of a high beam is changed by the manual switch, pattern (b) may be formed by slanting the both left shades 104RL and 104LL of the right and left variable shades 104R and 104L toward the discharge lamp 102 and by slanting both right shades 104RR and 104LR of the right and left variable shades 104R and 104L toward the projector lens 103.
When the vehicle headlight 100 is lit by an automatic switch, the following light distribution pattern may be changed by information from a camera, which is attached to a front window of a vehicle. When there is not an oncoming vehicle and a forward travelling vehicle in front of a vehicle, pattern (b) may be formed by the same method as the high beam. When an oncoming vehicle exists in a far forward direction of a vehicle, pattern (c) may be formed by slanting only the right shade 104LR of the left variable shade 104L toward the projector lens 103.
When an oncoming vehicle exists in a near forward direction of a vehicle, pattern (d) may be formed by slanting both right shades 104RR and 104LR of the right and left variable shades 104R and 104L toward the projector lens 103. When forward travelling vehicles exist in both far and near forward directions of a vehicle, pattern (e) may be formed by slanting only the left shade 104RL of the right variable shade 104R toward the discharge lamp 102. When a forward travelling vehicle exists in a left forward direction of a vehicle, pattern (f) may be formed by slanting both left shades 104RL and 104LL of the right and left variable shades 104R and 104L toward the discharge lamp 102.
Therefore, the vehicle headlight 100 can form the light distribution patterns (a) to (e) in accordance with surroundings such as the existence of an oncoming vehicle and a forward travelling vehicle. However, when the number of the light distribution patterns (a) to (e) further increases for additional patterns such as a light distribution pattern for a traffic sign, a light distribution pattern located near a vehicle for wet weather, etc., it may be difficult for the vehicle headlight 100 to increase additional patterns due to a constructive limitation.
Another conventional vehicle headlight using a matrix light source is disclosed in Patent Document No. 2 (Japanese Patent Application Laid Open JP2008-10228). FIG. 11 is a schematic side cross-section view showing the other conventional vehicle headlight, and FIG. 12 is a diagram showing exemplary light-emitting patterns formed by the matrix light source for the vehicle headlight of FIG. 11.
The conventional vehicle headlight 110 includes: a casing 111; the matrix light source 113 attached to the casing 111; a connector 115 connecting the matrix light source 113 for receiving a power supply and attached to the casing 111; an optical member 114 forming a matrix light emitted from the matrix light source 113; a transparent cover 112 passing the matrix light formed by the optical member 114 and attached to the casing 111.
The matrix light source 113 may emit a light-emitting pattern (a) for a high beam and a light-emitting pattern (b) for a low beam as shown in FIG. 12. Therefore, the conventional vehicle headlight 110 may form a light distribution pattern for a high beam similar to pattern (b) shown in FIG. 10 by light-emitting pattern (a) of the matrix light source 113, and may form a light distribution pattern for a low beam similar to pattern (a) shown in FIG. 10 by light-emitting pattern (b) of the matrix light source 113.
However, when the number of the light distribution patterns further increases, such as a light distribution pattern for a traffic sign, a light distribution pattern located near a vehicle for wet weather, and the like, it may be necessary for the vehicle headlight 110 to add additional light sources and/or to extend the optical member 114. Accordingly, the transparent cover 112 and the vehicle headlight 110 may become large, and also outside appearance possibilities for the vehicle headlight 110 may become diminished.
Another conventional vehicle headlight using a matrix mirror is disclosed in Patent Document No. 3 (Japanese Patent No. 3,982,412). FIG. 13 is a schematic side cross-section view showing the other conventional vehicle headlight, and FIG. 14 is a partial close-up perspective view showing the matrix mirror used for the vehicle headlight of FIG. 13.
The conventional vehicle headlight 120 includes: a light source 121; a reflector 122 reflecting light emitted from the light source 121; a collimator lens 123 passing the light emitted from the light source 121 and light reflected by the reflector 122; the matrix mirror 124 including a plurality of micro mirrors reflecting light L1 passing through the collimator lens 123; a diffusing lens 125 diffusing light L2 reflected by the matrix mirror 124; and a projector lens 126 projecting light diffused by the diffusing lens 125 in a light-emitting direction of the vehicle headlight 120.
In this case, the matrix mirror 124 includes the plurality of micro mirrors, for example 800×600 (=480,000 pieces). By digital-controlling the light L1 using the large number of micro mirrors so as to direct the light L2 toward the diffusing lens 125 for forming a light distribution pattern, various light distribution patterns similar to patterns (a) to (f) shown in FIG. 10 may be emitted via the projector lens 126 in accordance with a sensor, which detects an external condition of a vehicle.
However, the above-described structure in which the micro mirrors of 480,000 pieces are digitally-controlled at a duty ratio of, for example, 8 bit may become very complex. In addition, an alignment for the optical system such as the collimator lens 123, the matrix mirror 124 and the like may also become difficult and/or require high production and working tolerances.
The above-referenced Patent Documents are listed below, and are hereby incorporated with their English abstracts in their entireties.    1. Patent Document No. 1: Japanese Patent Application Laid Open JP2009-211963    2. Patent Document No. 2: Japanese Patent Application Laid Open JP2008-10228    3. Patent Document No. 3: Japanese Patent No. 3,982,412    4. Patent Document No. 4: Japanese Patent Application Laid Open JP2005-128147    5. Patent Document No. 5: Japanese Patent No. 4,092,283
The disclosed subject matter has been devised to consider the above and other problems, features, and characteristics. Thus, embodiments of the disclosed subject matter can include a variable light distribution unit using a semiconductor light source and a mirror that can provide various light distribution patterns with a compact structure. The disclosed subject matter can also include a vehicle headlight that includes a common light distribution unit forming a common light distribution pattern and the variable light distribution unit, which can form various light distribution patterns to enhance a visibility for a drive with a simple structure.